Do you mean something like http://ideone.com/? It's something I found the other day but haven't tried yet. I think it's probably more for testing some code snippet rather than working with a larger application, though. One I do use, however, is Adafruit's WebIDE for developing on the Raspberry Pi. http://learn.adafruit.com/webide/ Perfect solution for coding on the Pi and it's linked to Github/BitBucket.